The present disclosure relates to a transmission system and a transmission apparatus wherein a terminal such as a mobile apparatus is connected to a network without a cable, and particularly to a transmission system and a transmission apparatus wherein a mobile apparatus is connected to a wired network such as the Ethernet (registered trademark) through a connection apparatus such as an access point.
More particularly, the present disclosure relates to a transmission system and a transmission apparatus wherein a mobile apparatus is connected to a network at a transmission speed similar to that of the Ethernet (registered trademark), and particularly to a transmission system and a transmission apparatus wherein a mobile apparatus is connected to a network using short range communication means for communication at such a short distance as a contactless distance at a high speed with reduced power consumption and at a reduced cost.
The word “ubiquitous” is used frequently as a direction destined by a computer and a network in the future. “Ubiquitous” signifies an environment wherein, to anywhere the user moves, the user can utilize the capacity of computers individually having similar performances. For example, not only information equipments such as personal computers but also digital home electronics appliances, installation type AV equipments, digital still cameras and digital video cameras which are mobile apparatus, PDAs (Personal Digital Assistants) and portable telephone sets tend to be taken into the ubiquitous network. Under the ubiquitous environment, search for information and calculation are carried out by all of user's personal belongings and knowledge can be extracted easily.
In order to implement a ubiquitous environment, a great number of subjects are involved in hardware and software. First, as a hardware subject, a higher-speed and high-degree network is required in order to make it possible for various apparatus to immediately extract data necessary for the user.
The Ethernet (registered trademark) is known and widely utilized already as means for connecting various apparatus to each other into a network in a home or the like. The Ethernet (registered trademark) specifies layers corresponding to the physical layer and the data link layer which are two lower layers of the OSI reference model, and the 10Base-T having a 10-Mbps transmission speed, the 100Base-T having a 100-Mbps transmission speed and so forth are standardized. A standard group wherein a twist pair cable (twist pair cable) is used as a transmission medium from within the Fast Ethernet (registered trademark) standards is called 100Base-T and is standardized as IEEE 802.3u.
A principal LAN in the present age is configured from a combination of the Ethernet (registered trademark) which is physical standards and a TCP/IP protocol which specifies communication contents in a higher layer of the Ethernet (registered trademark). On the other hand, for mobile apparatus, it is popular to use a radio LAN in place of the Ethernet (registered trademark). This arises from reasons regarding the size of a connector of the Ethernet (registered trademark), convenience in use with cable connection and so forth. The radio LAN is standardized, for example, as IEEE 802.11. A terminal such as a mobile apparatus wherein the radio LAN is built in is mutually connected to the wire Ethernet (registered trademark) by bridging by means of a connection apparatus which is also called access point.
For example, some proposals have been made regarding a home network system to which an access point is connected through a server and the Internet and which is configured by connecting to a home terminal through a radio LAN (for example, refer to Patent Document 1).
FIG. 8 schematically shows a radio LAN incorporated in a terminal and a protocol stack in a connection apparatus which bridges a radio LAN and a wire LAN.
In FIG. 8, reference numeral 100 denotes a protocol stack on the mobile terminal side, and a PHY layer 102 defined by the IEEE 802.11 and a MAC (Machine Access Control) layer 103 are used as two lower layers. A plurality of standards such as a, b, g, and n exist in the IEEE 802.11 depending upon the difference in the used frequency band, modulation method and transmission speed and so forth. The higher layer 103 of the IEEE 802.11 MAC is configured from an LLC (Logical Link Control) layer, an IP (Internet Protocol) layer and a TCP (Transmission Control Protocol) layer, and an application layer 105 is provided as a higher layer than the layers just described.
Further, in FIG. 8, reference numeral 101 denotes a protocol stack of a connection apparatus corresponding to an access point or the like. A PHY layer 106, a MAC layer 107 and an upper layer 108 which are opposed to and communicate with the PHY layer 102 and MAC layer 103 on the terminal side are provided on the left side of the stack, that is, on the radio LAN side. A packet communicated by the radio LAN is bridged to a protocol stack of the wire Ethernet (registered trademark) on the right side through the PHY layer 106, MAC layer 107 and higher layer 108 by a bridge 109. Further, an upper layer 110, a MAC layer 111 defined by the IEEE 802.3 and a PHY layer 112 are provided on the right side of the stack, that is, on the Ethernet (registered trademark) side, and communication is carried out with an apparatus connected to the Ethernet (registered trademark) ahead the access point. With the protocol stack shown in FIG. 8, mutual connection between a mobile terminal and an equipment ready for the Ethernet (registered trademark) is implemented.
In this manner, by using the radio LAN, the mobile apparatus can be connected to a network. However, the transmission speed when wire communication is carried out through an access point depends upon the radio LAN standards, and approximately 20 Mbps to the utmost in throughput is a limit. Further, protocol conversion need be carried out between the IEEE 802.11 and the Ethernet (registered trademark) at an access point connected to a mobile apparatus, and the cost is required not only for protocol conversion but also for up-conversion of a transmission signal into a signal of a radio frequency band when transfer to the mobile apparatus is to be carried out.
Therefore, it is considered that, if an application wherein the transmission system shown in FIG. 8 is applied to reproduction of a digital video camera ready for the high definition television system, then the transmission speed when data is transmitted from the digital video camera to a connection apparatus by a radio LAN or protocol conversion carried out by the connection apparatus becomes a bottleneck, and a sufficient throughput cannot be obtained. Further, the radio LAN has a problem in that the power consumption is high and also the cost is high.
Although radio communication by a radio LAN or the like is utilized widely also in an ordinary household, different from mobile communication, such opportunities that image data is sent by radio while a digital still camera or a digital video camera is being moved are few. The inventors consider that, although many mobile apparatus are sufficient if they can carry out communication at such a short distance as a contactless distance although cable connection is not desirable, a transmission speed similar to that of the Ethernet (registered trademark) is demanded rather.
Patent Document 1: Japanese Patent Laid-Open No. 2002-162149
It is desired to provide a superior transmission system and a superior transmission apparatus by which a mobile apparatus can be connected suitably to a wired network such as the Ethernet (registered trademark) through a connection apparatus such as an access point.
It is also desired to provide a superior transmission system and a superior transmission apparatus by which a mobile apparatus can be connected to a network at a transmission speed similar to that of the Ethernet (registered trademark).
It is also desired to provide a superior transmission system and a superior transmission apparatus by which a mobile apparatus can be connected at a high speed, with low power consumption and at a low cost to a network using short distance communication means for communication at such a short distance as a contactless distance.